1. Field of the Invention
The invention relates generally to flashlights, and more particularly to a manually operable flashlight unit having a foot part fitting a finder shoe on a camera, standard contacts for chassis ground and flash release being arranged in the foot part.
2. Description of the Related Art
In flashlight units of this type, the flash is released by the camera via the so-called X contact, and the flash is switched off by a photodiode incorporated in the flashlight unit together with an evaluation electronic system as soon as a sufficient light intensity is reached. The adaptation to different lens diaphragms (apertures) and film speeds is performed via a change-over switch fitted on the flashlight unit.
The internal automatic switch-off device of the flashlight unit can also be disconnected so that the flash always shines with its full intensity. In the case of this so-called manual mode, the diaphragm must then be set manually at the lens in accordance with the desired range and film speed, in order to achieve the suitable brightening up from the flash.
Flashlight units integrated in compact cameras generally operate only in manual mode. The automatically setting diaphragm is calculated from the fixed guide number of the integrated flash and the measured range. The flash intensity and the flash duration are not controlled.
It is also known, for example from DE 32 21 856 A1, to arrange further contacts in the foot part of the flashlight unit and in the finder shoe of the camera in addition to the X contact. The available space is very restricted, with the result that at most two further contacts are provided in general. The position and importance of these contacts are usually specific to the company, while the shape of the foot part and finder shoe as well as the position of the contacts for the chassis ground in the respective outer molded part, and of the X contact in the central position, are fixed by an international standard. It is possible, for example, for the mounted flashlight unit to be switched on and a flash-ready signal to be sent to the camera via the further contacts.
When the flashlight unit is switched on, the flash capacitor integrated in the unit is charged in a certain time. When the necessary charge is reached, the flashlight unit transmits a signal to the camera via the flash-ready contact. Normally, the signal comprises a voltage level of a few volts with respect to ground, which, for example, is used for a display in the camera or triggers the shutter release. The designation AX contact has become established for this contact.
The flash power of separate flashlight units which can be mounted on the camera is substantially higher than that of a flashlight unit integrated in the camera, since the power supply via batteries and the installation space for charging capacitors in the camera are restricted. It is therefore desired also to be able to mount an external flashlight unit on cameras with an integrated flashlight unit. However, the problem arises in this case, on the one hand, of being able to disconnect the integrated flashlight unit as automatically as possible and, on the other hand, of switching the external flashlight unit into the same operating mode as the integrated flashlight unit. Given the multiplicity of already existing contact arrangements and dimensions, standardized overall, of the finder shoe, it is not possible in a technically sensible way to fit further contacts or switches. Moreover, additional contacts in the foot part of the flashlight unit would restrict its usefulness on different cameras.
The present invention is directed to overcoming or at least reducing the effects of one or more of the problems set forth above.